Device that is used for secure diffusion controlled display private copying and management of and conditional access to MPEG-4-type audiovisual content rights

ABSTRACT

A method for distributing video sequences according to a nominal flow format that describes a multiplicity of audiovisual scenes, each scene including a multiplicity of hierarchized audiovisual objects and a descriptor of the hierarchy and of spatial and temporal relationships among the objects, each video object including at least one complete I-VOP digital plane, including generating a first modified flow having the format of a nominal flow and a second flow of any format including digital information required for reconstruction of modified planes by analyzing the flow of video sequences, separately transmitting the two flows generated from a server to destination equipment, and calculating on the destination equipment a synthesis of a flow of the nominal format as a function of the first and second flows.

RELATED APPLICATION

This is a §371 of International Application No. PCT/FR03/00124, with aninternational filing date of Jan. 15, 2003 (WO 03/065731, published Aug.7, 2003), which is based on French Patent Application No. 02/01164,filed Jan. 31, 2002.

FIELD OF THE INVENTION

This invention pertains to the contingent access, secured broadcasting,control of recording, the private copying and the visualization ofaudiovisual data and television programs, or more generally anymultimedia program or sequence using an MPEG-4 type nominal flow format,by authorized users and proposes a secured system for the processing,access, broadcasting, delivery, recording, private copying,visualization and management of the rights of interactive video ormultimedia sequences.

BACKGROUND

The general problem is to provide a device capable of transmitting in asecured manner a set of films of high visual quality in an MPEG-4 formdirectly to a television screen and/or to be recorded on the hard diskof a box linking the remote transmission network to a monitor typescreen or television screen, while preserving the audiovisual quality,but preventing fraudulent use such as the possibility of making “pirate”copies of films or audiovisual programs recorded on the hard disk of thedecoder box.

With the presently available solutions, it is possible to transmit filmsand audiovisual programs in digital form via broadcasting networks ofthe airwaves, cable, satellite, etc. type or via telecommunicationnetworks of the DSL (Digital Subscriber Line) or LRL (Local Radio Loop)type or via DAB networks (Digital Audio Broadcasting). Moreover, inorder to prevent the pirating of the works broadcast in this manner,these works are often encrypted by various means known to the expert inthe field.

However, the principal drawback of presently available solutions (TiVoInc., WO 00/165762) is that it is necessary to transmit not only theencrypted data to the users, but also the decryption keys. Transmissionof the decryption keys can be implemented before, at the same time as orafter the transmission of the audiovisual programs. In order to increasethe security and thus the protection of the audiovisual works againstill-intentioned use, the decryption keys as well as the decryptionfunctions of the audiovisual decoders can comprise enhanced securitymeans such as smart cards or other physical keys that can optionally beupdated remotely.

Thus, the presently available solutions applied to a decoder box withthe possibility of local recording of audiovisual programs in digitalform on any kind of support of the hard disk or other type of memoryprovide the ill-intentioned user with the possibility of makingunauthorized copies of the program recorded in this manner, since at agiven moment the user possesses with a digital decoder box, optionallyassociated with smart card systems, all of the information, softwareprograms and data enabling the complete decryption of the audiovisualprograms. In fact, because the user has all of the data theill-intentioned user would have the possibility of making illegal copieswithout anybody becoming aware of this fraudulent copy at the moment itis made.

One solution would therefore consist of transmitting all or part of adigital audiovisual program solely on demand (on demand video services)via a broad band telecommunication network of the ADSL, cable orsatellite type, without authorizing the local recording of theaudiovisual programs. WO 00/11871 (Open Entertainment) thus proposes asolution of distribution of multimedia files on request by the user. Thedrawback is completely different and stems from the performance of thesenetworks which cannot ensure the continuous flow of multiple megabitsper second to each user as is required by the MPEG-4 flows which requirepass bands of several hundreds of kilobits to multiple megabits persecond.

Under these conditions, one solution consists of separating the flowinto two parts neither of which can be used on its own. Multiple patentshave been filed in this context. WO 99/08428 (Gilles Maton) discloses amultiapplication processing method of a localizable active terminal inwhich there is implemented at least one link with an identifiableprogram dedicated to the execution of an application, the programdictating its conditions of exploitation to the terminal for making thefunctions available. The terminal dialogues punctually by the use of alink with the management center for the implementation, if necessary, ofinputs and outputs of the center's capacity, the management centeroptionally becoming a slave of the terminal at the level of applicationof the incoming program. WO '428 also discloses a method foridentification of the program and terminal in exploitation mode. Thatmethod divides the flow into a part serving to identify the user and apart that contains the program itself. In particular, the program is notunusable, but merely locked out by the first part.

In another direction, EP 0778513 (Matsushita) describes a methodenabling the prevention of illegal use of an information unit by addingto it a control information unit in order to verify the user's rights.The system makes it possible to permanently know which part of theinformation unit is used and by which user and thus to know whether ornot this user is in an illegal position. That method thus secures thedata by adding to it additional information units which distort theinitial information.

WO 00/49483 (Netquartz) also provides methods and systems for creating alink between the users and an editor of digitized entities. The methodcomprises at least one of the following steps: the step of subdividingthe digitized entity into two parts; the step of storing one part inmemory in a memory zone of a server connected to a computer-basednetwork; the step of transmitting the other part to at least one userhaving available computer-based equipment; the step of connecting thecomputer-based equipment to the computer-based network; the step ofestablishing a functional link between the first part and the secondpart.

Finally, continuing this approach, U.S. Pat. No. 5,937,164 discloses asolution which consists of separating the flow into two parts, thesmaller of which holds an information unit required for the use of thelarger part. Nevertheless, that patent is not sufficient for respondingto the identified problem. In fact, the suppression of a part of theflow distorts the format of the flow and therefore cannot be recognizedas a standard flow that is exploitable with the general softwareapplications. This method of the prior art requires both a specificsoftware program at the server end, for the separation into two parts,and another specific software program to implement not only thereconstruction of the flow but also the acquisition of the principalflow and its exploitation according to a format proprietary to thesolution. This proprietary form is not the initial format of the flowprior to its separation into two parts in this known solution.

U.S. Pat. No. 5,892,825 follows on the preceding patent, but in a lessbroad framework because the flows are always encrypted. U.S. Pat. No.6,035,239 is based on the same principle and pertains to a methodenabling the reading of a CD-ROM or DVD-ROM type disk contingent on theidentification of the rights by the insertion of a smart card on whichthe information units necessary for reading are stored. That method isnot sufficient because it does not ensure that the modified flow is ofthe same format as the original flow. U.S. Pat. No. 6,185,306 pertainsto a method for the transmission of encrypted data from a Web site to arequestor computer. However, that method enables the user to haveavailable at a given moment all of the tools required for copying thedata.

U.S. Pat. No. 6,233,356 (Haskell Barin Geoffry et al.) discloses ascalability method of the MPEG-4 flows, i.e., the separation of theelements of the MPEG-4 video flow into multiple layers. The first layer,called the base layer, is required for reading the MPEG-4 flow andsufficient for reading it, but with a mediocre quality. The other layersmake it possible to improve this quality, but will only be transmittedto the decoder if the transmission means allow it, i.e., if it iscapable of transmitting, and the base layer and one or moresupplementary layers.

EP 0 920 209 (Thomson Multimedia) discloses a method and a device forthe scrambling of digital video data. EP '290 pertains to the change inthe I images of an MPEG-2 flow of the DC and AC coefficients in order toprotect the flow. The AC coefficients are permuted among each other inthe same block by means of an exchange value which will be contained inthe flow after the transformation has been implemented. The DCcoefficients will be replaced by the coefficients of different valuesselected by means of a control value which will also be stored in theflow.

WO 01/69354 (Microsoft) discloses a system which protects a digitalproduct (software or content) by breaking it down into at least twoflows. This first flow is transmitted to the client's equipment by aphysical medium such as a CD-ROM or a DVD. The second flow istransformed so as only to be exploitable by the client station inquestion, then it is transmitted by the same method or by atelecommunication network to this client station. The station receivingthe two flows can modify the first flow as a function of a keytransmitted by the server so that the first flow is compatible with thesecond flow received, and these two flows are recombined together inorder to reconstitute a binary flow with substance equivalent to theoriginal flow, but different in terms of configuration, and adequate forthe client system. Thus this system ensures that the flow to betransmitted is good for the client device and that it can only be usedby said device.

U.S. Pat. No. 6,104,860 (Goto Koicho et al.) discloses an access controlsystem enabling the recording or not of television programs as afunction of the authorization given to the user of this method, andvalidated by a key contained in a smart card. The transmitted televisionflow contains supplementary information units analyzed by the system andwhich validates or not the authorization to record. Once recorded, theflow can be replayed but it is again subjected to reading authorizationvia the access control.

“White Paper on the Secure Digital Music Initiative SDMI” (Rump N et al)discloses a system that consists of adding information to a flow inorder to add data concerning the ownership of said flow.

SUMMARY OF THE INVENTION

This invention relates to a method for distributing video sequencesaccording to a nominal flow format that describes a multiplicity ofaudiovisual scenes, each scene including a multiplicity of hierarchizedaudiovisual objects and a descriptor of the hierarchy and of spatial andtemporal relationships among the objects, each video object including atleast one complete I-VOP digital plane, including generating a firstmodified flow having the format of a nominal flow and a second flow ofany format including digital information required for reconstruction ofmodified planes by analyzing the flow of video sequences, separatelytransmitting the two flows generated from a server to destinationequipment, and calculating on the destination equipment a synthesis of aflow of the nominal format as a function of the first and second flows.

This invention also relates to the method wherein the VOP plane isbroken into blocks and macroblocks each dependent on each other bycorrelation coefficients, the first modified flow having I-VOP planesmodified by substitution of selected correlation coefficients bycoefficients of the same nature, but random, and the second flowincludes substituted correlation coefficients and the digitalinformation needed to enable the reconstruction of the modified planes.

This invention further relates to an apparatus for creating a video flowincluding at least one multimedia server containing original videosequences and a device for analyzing the video flow originating from theserver for generating the first and second flows.

This invention still further relates to an apparatus for exploiting avideo flow including a computer which is part of a communicationinterface for receiving a video flow originating from a communicationnetwork or a physical support reader, and equipped with at least onerecorder for storing the first flow, and a decoder including a displayinterface, communication means with the computer for receiving the firstflow transmitted by the computer and communication means for receivingthe second flow recomposing means for the original flow from the firstand second flows.

This invention yet again relates to a system for transmitting a videoflow including an equipment unit for production of a video flow, atleast one equipment unit for exploitation of a video flow and at leastone communication network between the production equipment unit and theexploitation equipment unit(s).

BRIEF DESCRIPTION OF THE DRAWINGS

Enhanced comprehension of the present invention will be obtained fromthe following nonlimitative example with reference to the attacheddrawings in which:

FIG. 1 is a diagram of the overall architecture of a system for theimplementation of a system for the implementation of the methodaccording to the invention,

FIG. 2 represents one particular mode of implementation of the analysisand flow synthesis system in accordance with the invention, and

FIG. 3 represents one particular mode of implementation of the flowsynthesis system in accordance with the invention.

DETAILED DESCRIPTION

This invention pertains to a method for the distribution of videosequences according to a nominal flow format constituted by datarepresenting a succession of audiovisual scenes constituted byaudiovisual objects hierarchized according to a script describing theirspatial and temporal relationships each comprising at least one I-VOPplane corresponding to a complete object plane such as is the case withthe MPEG-4 standard.

As is well known, the MPEG-4 standard introduces concepts of videoobjects (VO for “Video Object”), e.g., a person or car that passes. TheMPEG-4 standard also introduces the video object plane (VOP) whichrepresents a video object at a given moment and the video object layer(VOL). This decomposition into objects greatly facilitates interactivityand it becomes easier to obtain information on an object (the player orthe car that passes).

The basic principle of MPEG-4 compression is based on the content. It istherefore necessary to separate the background from the animatedobjects. The characteristic of MPEG-4 is to clearly separate the objectsand the background of a scene in order to later take advantage of thisfor the compression and supplementary functionalities that this lead to.This makes it possible, for example, in the case of a panoramic view toonly transmit the complete background once and to transmit separatelythe animated objects.

An MPEG-4 coded audiovisual scene is described as a set ofindividualized and independent elements. It contains base componentsgrouped together by type. These groups correspond to the branches of acut-out tree in which each leaf represents a simple base element. Thus,an audiovisual scene of MPEG-4 type should be understood as thecomposition of audiovisual objects according to a script describingtheir spatial and temporal relationships. The MPEG-4 functionalitiesrequire a representation environment or an architecture which uses adifferent data structure than MPEG-1 or MPEG-2 because the significantparts of the visual information must be accessible for interaction andmanipulation. In the text below, the term VOP (Video Object Plane)corresponds to a video component of arbitrary form. The VOP definitionplane has the task of defining the significant objects of the scene withwhich independent interactions and manipulations will be possible. Thismeans that these objects are represented in a manner to provide easyaccess preferably independent of the other objects of the scene.However, the different VOPs do not necessarily have the same spatial andtemporal resolutions.

Moreover, in order to increase the manipulation possibilities,hierarchies of VOPs associated with different degrees of accessibilityare also taken into account.

All of this enables the user to be able to interact with the objects ofthe scene. Here are several possible manipulations:

Modification of the spatial position of an object (VOP) in the scene;

Application of a spatial scale factor to an object of the scene;

Changing the speed with which an object moves in the scene;

Addition of objects;

Suppression of an object from the scene.

In the MPEG-4 standard, the information units relative to the form,movement and texture of the VOPs are coded in separate VOL (Video ObjectLayer) layers so as to enable separate decoding of the VOPs. WithMPEG-4, the rectangular image is merely one particular case of coding ofmultiple VOPs as an image of arbitrary form.

MPEG-4 VM (MPEG-4 Video Verification Model) uses an identical algorithmfor coding information relative to the form, movement and texture ineach layer. However, the information pertaining to the form is nottransmitted if the sequence to be coded does not contain standard imagesof rectangular size. In this case, the MPEG-4 video coding algorithm hasa structure similar to the MPEG-1 and MPEG-2 algorithms. This issuitable for applications that require a high degree of coding efficacywithout requiring extended functionalities based on the content.

The MPEG-4 compression algorithm is based on the hybrid technique of theDPCM/Transform already employed by the MPEG-1 and MPEG-2 standards.

The first VOP is coded in I-VOP mode. Each of the following images iscoded using the inter-image prediction (P-VOP). Only the data for theclosest previously coded image are used for the prediction. To this isadded the support of the B-VOPs. The coding method is the same as thatof the standard MPEG-1 and MPEG-2.

The incoming images that must be coded for each VOP layer are generallyof arbitrary form and the position and form of the images vary over timewith respect to a reference window. MPEG-4 VM thus introduces theconcept of VOP reference window with a macroblock grid adaptable to theform. All of the VOL layers that must be coded for an incoming videosequence are defined with reference to the reference window whose sizeis constant.

The information in the form of a VOP is coded prior to the coding of theposition vectors based on the macroblock grid of the VOP and isexploitable not only for encoding but also for decoding. In thesubsequent steps of the process, only the information pertaining to themovement and texture of the blocks of the macroblock are coded (whichcomprises the standard macroblocks and the contour macroblocks).

In its broadest sense, the invention pertains to a method for thedistribution of video sequences according to a nominal flow formatintended to describe a multiplicity of audiovisual scenes, each scenebeing constituted of a multiplicity of hierarchized audiovisual objectsand a descriptor of the hierarchy and of the spatial and temporalrelationships among the objects, each video object comprising at leastone complete I-VOP digital plane, characterized in that there isperformed prior to the transmission to the client equipment, an analysisof the flow in order to generate one first modified flow having theformat of a nominal flow and a second flow of any format comprising thedigital information required for the reconstruction of the modifiedplanes, then of transmitting separately the two flows generated in thismanner from the server to the destination equipment, and in that thereis calculated on the destination equipment a synthesis of a flow of thenominal format as a function of the first flow and the second flow.

The synthesis advantageously produces a flow rigorously identical to theoriginal flow, i.e. the method is without loss.

In one particular mode of implementation of this method, each videoobject comprises at least one N-VOP plane of the data representing theplane being calculated as a function of the differences between theN-VOP plane and at least one other plane.

The first flow advantageously has modified N-VOP planes.

According to one mode of implementation of this method, the data of atleast one N-VOP plane are calculated by movement compensation of theN-VOP plane in relation to the preceding N-VOP or I-VOP plane. The N-VOPplane is then referred to as P-VOP plane (predicted).

According to another mode of implementation of this method, the data ofat least one N-VOP plane are calculated by movement compensation of theN-VOP plane in relation to the preceding and following P-VOP and I-VOPplanes. The N-VOP plane is then referred to as B-VOP plane(bidirectional).

The format of the nominal flow is advantageously defined by the MPEG-4standard.

In one mode of implementation of this method, the first flow presentsmodified P-VOP planes.

In another mode of implementation of this method, the first flowpresents modified B-VOP planes.

The I-VOP plane is advantageously broken down into blocks andmacroblocks which are dependent on each other by correlationcoefficients and the first modified flow has I-VOP planes modified bythe substitution of certain correlation coefficients by coefficients ofthe same nature, but random, and that the second flow comprises thesubstituted correlation coefficients and the digital informationrequired for the reconstruction of the modified planes.

The analysis advantageously determines the correlation coefficients tobe modified as a function of the desired size for the second flow andthe desired degradation for the first modified flow. These modificationscan be: replace the correlation coefficients of an I-VOP plane with thecorrelation coefficients of another I-VOP plane, invert two correlationcoefficients of the same I-VOP plane, invert two correlationcoefficients of two I-VOP planes of the same flow, replace thecorrelation coefficients of an I-VOP plane by random values.

According to one particular implementation of this method, at least oneP-VOP plane is modified in the same manner as the I-VOP planes.

The analysis advantageously determines the I-VOP, P-VOP and B-VOP planesto be modified as a function of the size desired for the second flow andthe level of degradation desired for the first modified flow. Thesemodifications can be: modifications of the correlation coefficients ofthe I-VOP or P-VOP planes, replacement of a P-VOP plane by another P-VOPplane of another flow, inversion of two P-VOP planes of the same flow,inversion of a B-VOP plane and a P-VOP plane of the same flow.

If there are B-VOP and P-VOP planes, an N-VOP plane is necessarily ofthe B-VOP or P-VOP type.

In one particular implementation of this method, the transmission of thefirst flow is implemented via a material support distributed physicallysuch as, e.g., a CD-ROM, DVD, hard disk or flash memory card.

In another implementation of this method, the transmission of the firstflow is implemented via a broad-band network (cable, satellite, opticalfiber, airwaves, DSL, DAB).

According to the implementation of this method, the transmission of thesecond flow is implemented via a cable network, via a switchedtelephonic network (analog or digital PSTN), via a mobile telephonenetwork using the GSM, GPRS or UMTS standards, via a LRL network (localradio loop) or via a DSL network.

According to one particular variant of this method, the transmission ofthe second flow is implemented via a broad-band network of the same typeas the network used for the first flow, or in fact via the same network.

According to one particular variant of this method, the transmission ofthe second flow is implemented by means of a flash memory card or bymeans of a smart card.

The transmission of one or both of the two flows is advantageouslyencrypted.

One or both of the two flows is advantageously watermarked usingconventional watermarking techniques.

According to one mode of implementation of this method, the twogenerated flows can be sent to a single equipment unit, a group ofequipment units or to all of the equipment units.

According to one particular mode of implementation, the reconstructionis contingent on a transaction.

The reconstruction can also be authorized by a consultation of a privatecopy requested by the client.

Generally speaking, the fact that the reconstruction is contingent onthe authorization of the portal allows any operator of the service tomanage all of the rights attached to the audiovisual works.

The invention moreover pertains to an equipment unit for the creation ofa video flow for the implementation of this method comprising at leastone multimedia server containing the original video sequences andcharacterized in that it comprises a device for analysis of the videoflow originating from the server in order to generate the two flows.

This equipment advantageously comprises a memory for recording a“private copy” marker indicating for each sequence the rights of eachuser: private copy that can be watched an unlimited number of times,private copy that can be watched a limited number of times andspecification of that number, private copying prohibited.

The invention moreover pertains to an equipment unit for theexploitation of a video flow for the implementation of this methodcomprising a standard flow decoder, at least one recording interface(hard disk, flash memory) for storing the content of said first flowand/or a disk reader (CD, DVD, etc.) and at least one display interface(standard screen, wireless screen, video projector), characterized inthat it comprises a means for the recomposition of the original flowfrom the two flows.

According to one particular mode of implementation, the means is asoftware program application installed on the equipment unit.

According to another mode of implementation, the means is a fixedelectronic device.

According to another mode of implementation, the means is a portable(mobile) electronic device with an incorporated screen.

According to one mode of implementation in which the equipment isinstalled on a computer, the means uses a resource specific to theproduct (card) in order to prevent the copying of the temporaryinformation of the second flow on a permanent support.

The recording interface advantageously also stores a “private copy”marker in relation to the first flow indicating the user's rights forthis sequence: private copy that can be watched an unlimited number oftimes, private copy that can be watched a limited number of times withspecification of this number, and private copying prohibited.

According to another mode of implementation, the means is a fixedelectronic device.

According to another mode of implementation the means is a portable(mobile) electronic device with an incorporated screen.

According to one mode of implementation in which the equipment isinstalled on a computer the means uses a resource specific to theproduct (card) in order to prevent the copying of the temporaryinformation of the second flow on a permanent support.

The recording interface advantageously also stores a “private copy”marker in relation to the first flow indicating the user's rights forthis sequence: private copy that can be watched an unlimited number oftimes, private copy that can be watched a limited number of times withspecification of this number, and private copying prohibited.

The equipment advantageously comprises a smart card reader foridentifying the user.

The equipment advantageously comprises a smart card reader, with thesmart card containing the software applications.

The equipment advantageously comprises a smart card reader, with thesmart card containing the second flow for a given content.

One variant of implementation consists of making the client equipment inthe form of two means interconnected by a physical link or a remote link(Bluetooth, AirPort, WIFI, infrared, etc.). According to this variant,the equipment for the exploitation of a video flow comprises a firstmeans constituted of a personal computer of a communication interfacefor receiving a video flow stemming from a communication network or aphysical support reader, and equipped with at least one recording means(hard disk) intended to store the content of the first flow, and asecond means constituted of a decoder, comprising a display interface,means for communication with the principal computer for receiving thefirst flow transmitted by the computer and communication means forreceiving the second flow, as well as a means for the recomposition ofthe original flow from the two flows.

According to a first mode of implementation, the means for therecomposition of the flow is a software application installed solely onthe decoder.

According to a second mode of implementation, the means for therecomposition of the flow is an electronic device installed solely onthe decoder.

The invention lastly pertains to a system for the transmission of avideo flow, characterized in that it comprises an equipment unit for thecreation of a video flow, at least one equipment unit for theexploitation of a video flow and at least one communication networkbetween the production equipment and the exploitation equipment unit(s).

The invention pertains to a data flow in a nominal format especially,but not exclusively an MPEG-4 type flow. The form of the audiovisualflow used must have the following characteristics:

This format must break down the data into frames, each frame comprisingone complete I-VOP plane and at least one P-VOP plane calculated bycoding the differences (movement compensation) between this plane andthe preceding I-VOP or P-VOP plane; and

Each frame optionally comprises at least one B-VOP plane calculated bycoding the differences (movement compensation) between this plane andthe preceding or following I-VOP and/or P-VOP planes.

The invention pertains to a data flow of nominal format, especially, butnot exclusively an MPEG-4 type flow. The format of the audiovisual flowemployed must have the following characteristics:

this format must break down the data into frames, each frame comprisingone complete I-VOP plane; and

each I-VOP plane contains correlation coefficients between the differentblocks and/or macroblocks of the I-VOP planes.

In the description below, the example pertains to an MPEG-4 flow withoutthereby constituting a limitation on the scope of protection.

The general principle of a method for making a video flow secure ispresented below. The objective is to authorize video on demand andcard-paid video services via all of these broadcast networks and thelocal recording in the user's digital decoder box. The solution consistsof preserving permanently outside of the user's habitation, in thebroadcast and transmission network, a part of the recorded audiovisualprogram, this part being essential for displaying the audiovisualprogram on a television screen or other type of monitor, but of a verysmall volume in relation to the total volume of the digital audiovisualprogram recorded by the user. This missing part will be transmitted tothe transmission broadcasting network at the moment of visualization ofthe previously recorded digital audiovisual program by the user.

The larger part of the audiovisual flow will thus be transmitted via aconventional broadcast network while the missing part will betransmitted on demand via a narrow band telecommunication network suchas the conventional telephone networks or cellular networks of the GSM,GPRS or UMTS type or using a small part of a network of the DSL or LRLtype, or by using a subset of the shared pass band on a cable network.

In FIG. 1, the setup of the video interface (8) is adapted to link atleast one display device, e.g., a monitor, a video projector or atelevision screen type device (6), to at least one broad-bandtransmission and broadcasting network interface (4) and at least onetelecommunication network interface (10). This setup is composed of amodule (8) comprising principally on the one hand a processing unit forprocessing, in particular decoding and unscrambling, any MPEG-4 typevideo flow according to a preloaded decoding and unscrambling softwareprogram in a manner so as to display in real time or on a delayed basis,to store, to record and/or to transmit on a telecommunication networkand, on the other hand, at least one screen interface (7) and aninterface for connection to a local or extended network (5) and/or (9).The broad band transmission and broadcasting network (4) and thetelecommunication network (10) can be merged into a single network.

The hard disk of the module (8) can be used as buffer memory formomentarily storing at least a part of the video program or sequence tobe displayed, in the case of delayed visualization or of limitation inthe pass band of the transmission network. The visualization can bedelayed or deferred at the request of the user or the portal (12).

As shown in FIG. 1, the connection interface (5) is linked to abroad-band transmission and broadcasting network (4) such as a modem, asatellite modem, a cable modem, an optical fiber line interface or aradio or infrared interface for wireless communication.

It is by means of this conventional video broadcast link that thecontents of the audiovisual programs such as films will be transmitted.However, in order to not allow pirate copies to be made beforetransmitting the audiovisual content from the server (1) or the portal(12) it is provided to hold back a small part of the audiovisual contentin the portal (12).

In the case of visualization of an audiovisual program in real time,this small part of the audiovisual content preserved in the portal (12)will also be transmitted to the module (8) via the telecommunicationnetwork (10).

Since the successive planes of a video sequence contain a large numberof identical visual elements (as in cinema, an image resembles thepreceding image), MPEG-4 only records the elements that differ from theoriginal plane. Thus an entire reference plane will be modified bypreserving the modifications brought to the coefficients in the portal(12) and, for the successive planes which are dependent on this I-VOPreference plane, it not necessary to bring the modifications becausethey will cause divergence of the visualized flow because of thedisturbances brought to the I-VOP reference planes.

The MPEG-4 compression thus commences initially by breaking down theimage into different square matrices comprising multiple points orpixels, each one having its own calorimetric value. A calculationprovides a mean value for each matrix within which is now embedded eachpoint. This processing generates a pixilation and the appearance ofuniform flat tints where there existed tint nuances. The second stop ofthe MPEG-4 compression consists of preserving from one plane to anotheronly the changing elements.

In order to obtain animated images of the MPEG-4 type, the principleconsists of capturing several images in time, the intermediary imagesbeing calculated from these. The analysis of the complete referenceplanes (called I-VOP for Intra) makes it possible to predict theintermediary P-VOP planes (Predicted). Then the B-VOP planes(Bidirectional) are intercalated between reference planes and predictedplanes.

The video is represented as a succession of individual planes each ofwhich is processed as a two-dimensional matrix of image elements(pixels). The representation of the colors of each pixel comprises threecomponents: a luminance component Y and two chrominance components Cband Cr.

The compression of the digitized video is implemented by multipletechniques: subsampling of chrominance information to adapt to thesensitivity of the human visual system (HVS), quantification, movementcompensation (MC) to exploit temporal redundancy, transformation in thefrequency domain by discrete cosine transformation (DCT) to exploit thespatial redundancy, variable length coding (VLC) and imageinterpolation.

Since the human visual system (HVS) is most sensitive to the resolutionof the luminance component of an image, the Y pixel values are coded atfull resolution. The human visual system is less sensitive tochrominance information. Subsampling eliminates the values of pixelsbased systematically on position which reduces the amount of informationto be compressed by other techniques. The standard preserves a set ofchrominance pixels for each 2×2 neighborhood of luminance pixels.

The base coding unit of an image is the macroblock. The macroblocks ofeach image are coded successively from left to right and from top tobottom. Each macroblock is composed of six 8×8 blocks: four luminanceblocks, one Cb chrominance block and one Cr chrominance block. It shouldbe noted that the four luminance blocks cover the same zone of the imageas each of the chrominance blocks because of the subsampling of thechrominance information performed to adapt the coding to the sensitivityof the human visual system.

For a given macroblock, the first operation is the selection of thecoding mode which is dependent on the type of image, the efficacy of thecompensated movement prediction in the coded region and the nature ofthe signal contained in the block. Secondly, a compensated movementprediction of the content of the block, based on the prior or futurereference images, is formed. This prediction is subtracted from the realdata of the current macroblock in order to form an error signal.Thirdly, this error signal is divided into six 8×8 blocks (4 luminanceblocks and 2 chrominance blocks in each macroblock) to each of which isapplied a discrete cosine transformation. The resultant 8×8 block of DCTcoefficients is quantified. The resultant two-dimensional block isscanned in a zigzag manner to be converted into a one-dimensional chainof quantified DCT coefficients. Fourthly, the annexed information of themacroblock (type, vectors, etc.) as well as the data of the quantifiedcoefficients are coded. In order to attain a maximal efficacy, a certainnumber of variable length coding tables are defined for the differentdata elements. A coding of the field lengths is applied to thequantified coefficients data.

The DCT coefficient of the upper left point (0,0) of the blockrepresents a zero horizontal and vertical frequency: it is referred toas DC coefficient (continuous). Since the DC coefficient is proportionalto the mean value of the pixels of the 8×8 block, the predictive codingenables a supplementary compression because the difference in the meanvalues of the neighboring 8×8 blocks tends to be relatively small. Theother coefficients represent one or more nonzero horizontal and/orvertical spatial frequencies and are referred to as AC coefficients. Inorder that the level of quantification of the coefficients correspondingto the high spatial frequencies favor the creation of a zerocoefficient, one selects a quantification pitch such that the humanvisual system (HVS) is unlikely to perceive the loss of spatialfrequency in question, unless the value of the coefficient is above thisquantification level. The statistical coding of the predictedcoefficient fields of high consecutive order of zero value contributesconsiderably to the compression gain. In order to group together thenonzero coefficients at the beginning of the series and to code as manyzero coefficients as possible following the last nonzero coefficient,their sequence is given by a zigzag scanning which concentrates theirhigh spatial frequencies at the end of the series.

Variable length coding (VLC) is a statistical coding technique whichassigns the code words to the values to be coded. Short code words areassigned to frequency values with a high level of occurrence and longcode words are assigned to those with a low level of frequency. Morefrequent short code words are on average predominant such that the codedchain is shorter than the original data.

The invention consists of using the correlation between the DC and/or ACcoefficients in an I-VOP plane in order to be able to manipulate thevisual appearance and validity of the sequence to which belongs theI-VOP plane in question.

In the subsequent text, the manipulations brought to the DC coefficientscan also be brought to the AC coefficients without it being necessary toprovide specifications in greater detail.

In fact, given that the I-VOP planes are the principal carriers ofinformation in an MPEG-4 sequence, all important modifications affectingthese I-VOP planes will necessarily have an impact on the validity ofthe sequence.

Thus, the possibility of obtaining noteworthy degradations of the I-VOPplanes without effecting complicated manipulations is offered by thecorrelation between the DC coefficients in this I-VOP plane. Thesecoefficients, being highly dependent on each other, determine to a greatextent the value of the following coefficients of the same type. It isthus that by modifying the information contained therein that onemodifies profoundly the I-VOP planes and as a consequence the entireMPEG-4 sequence that follow this I-VOP plane.

Each macroblock of an I-VOP plane contains six blocks, each of whichcommences with a DC coefficient. Four blocks correspond to the luminance(Y) and two blocks correspond to the chrominance (C) of the macroblock.The value written in a file of the MPEG-4 flow representing a DCcoefficient is in effect the difference between the real value of thiscoefficient and that of the corresponding coefficient which precedes itand which, for the Y blocks, can be found in the same macroblock or inthe preceding macroblock whereas for the C blocks it is always in thepreceding macroblock. A modification of one of these differences willautomatically lead to a modification of the information in all of thesubsequent macroblocks.

When it reads the binary train, a conventional MPEG-4 decoder identifiesthe beginning of a coded plane, then the type of plane. In order toprevent any confusion with a standard decoder box often referred to as a“Set Top Box or STB”, the standard MPEG-4 decoder will be referred to as“Reader” (“Player” or “Viewer”) in the continuation of this document.This Reader can be implemented in hardware and/or software form. TheMPEG-4 reader decodes successively each macroblock of the plane. Theplane is reconstructed when all of these macroblocks have beenprocessed. In the case of an I-VOP plane, it constitutes a referenceplane for the subsequent planes and it is stored in the place of theoldest reference plane. The planes are thus available in digital formfor post-processing and display in accordance with the application.

In the case of an MPEG-4 type audiovisual program, not all of thecharacteristics of the I-VOP planes originating from the server (1) orportal (12) are transmitted to the module (8). In particular, thecharacteristics in accordance with the invention are the DC correlationcoefficients contained in the I-VOP planes.

Certain DC coefficients of these I-VOP planes are preserved in theportal (12). In contrast, in place of the DC coefficients of theseuntransmitted I-VOP planes, the device according to the invention willintercalate false DC coefficients of the same nature as the DCcoefficients taken and preserved in the portal (12) such that thestandard MPEG-4 Reader of the module (8) is not disturbed by thesemodifications that it will be unaware of and will reconstitute in theoutgoing stream an output MPEG-4 flow which will be incorrect from thevisual point of view for a human being but correct from the MPEG-4format point of view.

The MPEG-4 Reader of the box (8) is a standard MPEG-4 Reader and has notbeen in any way modified or affected by the changes brought to the I-VOPplanes.

Moreover, in the case of an MPEG-4 type audiovisual program, it isprovided to not transmit all of the B-VOP and/or P-VOP planesoriginating from the server (1) or portal (12) to the module (8). TheseB-VOP and/or P-VOP planes are stored in the portal (12). In contrast, inplace of the untransmitted B-VOP and/or P-VOP planes, the deviceaccording to the invention will intercalate false B-VOP and/or P-VOPplanes of the same nature as the I-VOP and/or P-VOP taken, substitutedand preserved in the portal (12) such that the MPEG-4 Reader of themodule (8) is not disturbed by these modifications of which it isunaware and it will reconstitute on an outgoing basis an MPEG-4 outputflow which will be incorrect from the visual point of view for a humanbeing but correct from the MPEG-4 format point of view.

The MPEG-4 Reader of the box (8) is a standard MPEG-4 Reader and has notin any manner been modified or affected by the changes brought to theB-VOP and/or P-VOP planes.

According to one particular mode of implementation, in order to increasethe efficacy of the protection system, it is preferable to not transmitthe B-VOP and/or P-VOP planes which are the closest and which follow theI-VOP planes of the MPEG-4 flow. For an even greater efficacy, afteranalysis of their volume and their weight in octets or in bits, theB-VOP and/or P-VOP planes will be selected to not be transmitted butpreserved in the portal (12).

According to one particular mode of implementation, certain P-VOP and/orB-VOP planes will be permuted with each other.

As shown in FIG. 1, the connection interface (9) is linked to anextended telecommunication network (10) directly or via a local networkfunctioning as an access network and is constituted, for example, of asubscriber line interface (analog or digital telephone network, DSL,LRL, GSM, GPRS, UMTS, etc.).

Thus the audiovisual programs are broadcast in a conventional manner inbroadcast mode via the broad band transmission network (4) of theairwaves, cable satellite, digital airwaves, LRL, etc. type directlyfrom the server (1) via the link (3 bis) or via the portal (12) via thelink (2) and (3) to the decoder module (8) by means of the link (5).Each audiovisual program broadcast in this manner can be optionallyencrypted and, in accordance with the present invention, the MPEG-4flows will comprise modifications at the level of certain I-VOP planesas described above. As a function of the parameters selected by the useror of information transmitted by the broadcast server, certainaudiovisual programs modified in this manner and incomplete are recordedon the hard disk of the box (8).

When the user wants to watch an audiovisual program recorded in thismanner on the hard disk of decoder module (8), the user implements therequest in the conventional manner via the remote control linked to thedecoder module (8) which then connects automatically to the portal (12)via the link (9) of the local network or direct access type and via thetelecommunication network (10) itself linked to the portal (12) via theconnection (11). During the entire visualization of the audiovisualprogram, the links (9) and (11) remain established and enable thedecoder module (8) to receive the functions and parameters ofrestoration of the modified DC coefficients of the I-VOP planes. Themodified DC coefficients of the I-VOP planes transmitted in this mannerare never recorded on the hard disk of the decoder module (8) becausethe reconstituted I-VOP planes are directly displayed on thevisualization screen (6) via the link (7) after having been processed bythe Reader of the decoder module (8) from its local volatile memory.After having been processed and visualized, the modified and/or missingDC coefficients of the I-VOP planes that have been transmitted by theportal (12) will be erased from the local volatile memory of the decodermodule (8).

According to one particular mode of implementation, the modified DCcoefficients of the I-VOP planes broadcast in this manner can beoptionally encrypted by any presently existing or future encryptionmeans. The same is true for the algorithms, functions and restoration oforder of the modified DC coefficients of the I-VOP planes.

Each time that the user wants to watch a program recorded on the harddisk of the decoder module (8), the decoder module (8) is connectedautomatically to the portal (12). Similarly when the user implements apause, the transmission of modified DC coefficients of the I-VOP planesoriginating from the portal (12) will be interrupted until therestarting of the visualization, thereby ensuring that not all of theinformation of an audiovisual program will be found in the decodermodule (8) at a given moment and thereby preventing ill-intentionedpeople from making pirate copies of these recordings.

According to one particular mode of implementation, the decoder module(8) comprises a smart card reader which enables the portal (12) toauthenticate the user/owner of the decoder module (8).

According to one particular mode of implementation, for a given MPEG-4content, the smart card contains said second flow which was stored inmemory by the portal (12).

If this is authorized, the smart card also allows the user to createprivate copies of the audiovisual programs recorded on the hard disk ofthe decoder module (8). In order to implement this, if the user wants tomake a private copy of an audiovisual program, he will do it in theconventional manner on a VCR via the link (7) which connects the module(8) to the display screen (6).

However, if he wants to save a private copy on the hard disk of his box,he will so inform the module (8) which will record the “private copy”information unit as well as the user's coordinates from the smart cardin a particular field (84) of this audiovisual program recorded on thehard disk (85) of the decoder module (8). Subsequently, each time thatthe user wants to watch this private copy, the module (8) willautomatically connect to the portal (12) and inform the portal that theuser wants to read his private copy; in response, if the reading of theprivate copy is possible for this user which possesses this smart cardlinked to this decoder module (8), the decoder module (8) will thenreceive the modified and/or missing DC coefficients of the I-VOP planesas well as all the other information enabling the visualization of theaudiovisual program constituting the private copy.

According to another mode of implementation, if the user wants to save aprivate copy on the hard disk of his box, he will so inform the serverwhich will record the information unit “private copy” for this programin the private copy memory (124) of the portal (12) and for this userauthenticated by the smart card. Subsequently, each time that the userwants to watch this private copy, the decoder module (8) will connectautomatically to the portal (12) and inform the portal that the userwants to read his private copy. In response, if the reading of theprivate copy is possible for this user which possesses this smart cardand for this program, the decoder module (8) will then receive themissing DC coefficients of the I-VOP planes as well as all of the otherinformation enabling visualization of the audiovisual programconstituting the private copy.

According to one particular mode of implementation, the so-called“private copy” could allow the user to watch this audiovisual program inan unlimited manner or in a number of times determined in advance by theservice provider which authorized this private copy.

The invention also pertains to the decoder module (8) used by theconsumer for accessing the data. This physical box is located in theuser's domicile. It provides a set of functionalities which manage theinformation suitable for presentation according to the selection of theaudience and manages the connection and communication with the remoteserver.

According to one particular mode of implementation, the physical boxcorresponding to the video interface setup is implemented by means of afixed autonomous device with integrated hard disk.

According to one particular mode of implementation the physical boxcorresponding to the video interface setup is implemented as a portable(mobile) autonomous device with integrated hard disk and/or disk reader(CD, DVD, etc.).

According to one particular mode of implementation the autonomousphysical box comprises a smart card reader.

According to another particular mode of implementation the videointerface setup is implemented as an add-on card which will be installedin a PC and will be linked to at least one broad band transmission andbroadcasting network interface (4) and to at least one telecommunicationnetwork interface (10). This card will use the hard disk of the PC forrecording the first flow but will have its own calculator and volatilememory so as to not allow the ill-intentioned PC user the means toaccess the complementary information such as the modified PCcoefficients of the I-VOP planes of the second flow.

According to the present invention, the video and multimedia servers (1)and/or (12) comprise means for coding, transcoding and scrambling videodata, particularly means for adding cryptographic and securityinformation units at the beginning and all along the sequences.

Finally, it should be noted that the invention degrades the MPEG-4 flowfrom the visual point of view to the point of not allowing recognitionof the transmitted and displayed scenes if there is no access to thecomplementary data and characteristics, but completely reconstitutes theM-PEG4 flow in the video interface setup without any loss.

Although the present invention is most particularly focused onaudiovisual data, it is understood that all interactive multimediainformation and all interactive data can be processed by the presentsetup and the present system, the MPEG-4 type video data being the mostelaborated.

Better comprehension of the invention will be obtained from thedescription below which presents the physical basis of the inventionwith reference to FIG. 2 of the attached drawings representing apreferred mode of implementation of the invention as a nonlimitativeexample of implementation particularly suitable for cable and satellitenetworks. The complete MPEG-4 flow (101) is analyzed by the analysisdevice (121) of the portal (12) and will thus be separated into anMPEG-4 type flows but whose missing DC coefficients of the I-VOP planeswill have been processed and transmitted via the output (122) of theportal via the broad band broadcast transmission network (4).

The other part of the modified MPEG-4 flow will be stored in memory inthe buffer memory (122) of the portal (12). For each MPEG-4 flowbroadcast in this manner, the portal (12) will store in a buffer memory(122) the modifications which had been implemented on this MPEG-4 flowby the analyzer (121) of the portal (12). It should be indicated thatfor the same incoming MPEG-4 flow (101), the processing of the flow canbe different for each decoder module/user (8) and/or for each group ofdecoder modules/users (8). The buffer memory (123) of the portal (12)therefore has a different memory zone for each user.

In the implemented examples, for a first user, the DC coefficients ofcertain I-VOP planes of the MPEG-4 flow are modified. For a second user,certain coefficients of the I-VOP planes and certain P-VOP planes of theMPEG-4 are modified. For a third user, certain P-VOP planes and certainB-VOP planes of the MPEG-4 flow are substituted, modified and/orexchanged; in the fourth example, the decoder module (8) is portable(mobile).

We will now described in detail the different steps for the first user.

The portal (121) selected the MPEG-4 flow (101) that it must send to thedecoder module/user (8) 50 that the user can watch it on a delayed basison television screen (6). This user is linked to a digital cablebroadcasting network (4) and an ADSL telecommunication network (10).

The analysis system (121) of the portal (12) will thus read the incomingMPEG-4 flow (101) and each time it detects an I-VOP plane, it will breakit down into macroblocks (thus into slices), then into blocks. Thisanalysis allows it to recognize in the code the DC coefficients and tosubstitute certain among them with random values in order to render theplanes (and by consequence the sequence) unreadable from the humanvision point of view. The true values of the DC coefficients will bestored in the output buffer (123) which will subsequently enable thereconstitution of the original sequence in the decoder module (8), byfollowing an inverse schema. In the implemented example, one of everytwo macroblocks comprises a modified block (DC coefficient) while stillrespecting the modification frequencies for the six blocks of amacroblock.

The analysis system (121) then writes the value of the substitutedcoefficient of the modified I-VOP plane in the buffer (123). Theanalysis system continues its analysis until the end of the incomingMPEG-4 flow.

The new modified MPEG-4 flow is then recorded in the output buffer (122)to be broadcast on the broadcast network (4) via the link (5). Thesubstituted DC coefficients of the modified I-VOP planes of the incomingMPEG-4 flow (101) are stored in memory in the buffer (123) of the portal(12).

During this time and in a completely unsynchronized manner, the modifiedMPEG-4 output flow originating from the output buffer (122) of theportal (12) is broadcast via the broad-band network (4) to one or moredecoder modules (8).

Each authorized decoder module (8) that wants to record this therebymodified MPEG-4 flow can then read this MPEG-4 flow and record it on itshard disk (85). This recording initiative is left to the decoder module(8) under the control of the portal (12). In order to implement this,the analysis system (121) had written at the beginning of the MPEG-4flow an information unit of supplementary data which specified thedestination addresses of this modified MPEG-4 flow. The destinations canthus be a single addressee/user by himself, a group of or all of thedecoders modules (8) connected to the network (4).

The phase described above corresponds to the first phase of preparationof the MPEG-4 flow by the portal (12), to its transmission via thebroad-band network (4) and to its recording in a decoder module (8).This decoder can then display this MPEG-4 flow recorded on its hard disk(85). In order to implement this, the synthesis system (87) of thedecoder module (8) will read the MPEG-4 file from its hard disk (85) andwill send it to a conventional MPEG-4 reader (81). If no complementarydata is received by the synthesis system (87), then the MPEG-4 flowwhich reaches the reader (81) is processed and displayed as it is, whichcauses a major distortion of the display on the visualization screen(6). In fact, the modified I-VOP planes which are processed by thesynthesis system (87) do not correspond to the I-VOP planes which arenecessary for a correct visualization since certain DC correlationcoefficients were substituted by random coefficients. On the other hand,since the recorded flow is clearly an MPEG-4 type flow, the reader (81)does not recognize any difference and displays the information on theoutput screen (6) which appears as an MPEG-4 data flow but totallyincoherent for the human who watches the screen (6). Any copy of theMPEG-4 flow originating from the hard disk (85) of the decoder module(8) will produce the same visual effect upon its reconstitution by anyMPEG-4 reader; any use of this copy which would be ill intentioned wouldthus be doomed to failure.

When the user of the decoder module (8) wants to truly visualize onscreen (6) the audiovisual program recorded on hard disk (85), the usersends a request to the synthesis system (87) with a remote control aswith a VCR or DVD player having a menu on a television screen. Thesynthesis system (87) then sends a request to the hard disk (85) andbegins to analyze the modified MPEG-4 flow originating from the harddisk (85) via the reading buffer (83). The synthesis system (87) thenestablishes a link with the portal (12) via the telecommunicationnetwork (10) which is a DSL link in our example. Once this link has beenestablished and during the entire duration of the visualization of thefilm or audiovisual program, the synthesis system (87) draws out fromthe buffer memory (123) of the server (12) the substituted correlationcoefficients and the data corresponding to the modified I-VOP planes ofthe flow recorded on the hard disk (85). These correlation coefficientsand these position data originate from the synthesis system (87) via theinput buffer memory (86) and are stored temporarily in the volatilememory (88) of the synthesis system (87). From the modified MPEG-4 flowwhich arrives via the buffer (83) and from the correlation coefficientsand the associated data which come from the buffer (86) in the memory(88), the synthesis system (87) reconstitutes in inverse manner of thepreviously described analysis process the I-VOP planes modified by thereal I-VOP planes, and sends the new MPEG-4 flow reconstituted in thismanner to the reader (81) to be correctly displayed on the screen (6).Upon their use, the correlation coefficients to be substituted and theassociated date of these I-VOP planes are erased from the volatilememory (88).

In the implemented example, before the portal (12) authorizestransmission of the I-VOP planes and associated data from its buffer(123), the portal (12) must verify that the user of the decoder module(8) is clearly authorized to implement the transaction. In order to dothis, the portal (12) reads the information contained on the smart card(82) of the decoder module (8) and verifies that this user is in factauthorized to watch this audiovisual program. It is only after thisverification that the correlation coefficients and the associated dataare sent from the buffer (123) to the decoder module (8) correspondingto this user via the network (10).

In the implemented example, the user also made a private copy of theaudiovisual program. The synthesis system (87) therefore wrote in a part(84) of the hard disk (85) complementary data as well as the number ofthe smart card (82) and the information unit “private copy” as dataassociated with this audiovisual program. Upon the next private readingof this audiovisual program, the synthesis system (87) will analyzethese associated data and thereby inform the portal (12) that the userof the decoder module (8) is reading the private copy. If this functionis authorized for this decoder module/user (8) by the portal (12), thecorrelation coefficients and associated data will then by sent by theportal (12) to the buffer (86) as described above. In the contrary case,the correlation coefficients and the associated data will not betransmitted and the user of the decoder module (8) will not be able towatch the reconstituted MPEG-4 flow.

We will now describe in detail the different steps for the second userof decoder module (8).

In this second case, the broadcast network (4) is a satellite networkand the telecommunication network (10) is a cellular telephony system ofGSM type narrow pass band.

In a manner identical to that described above, the user of the decodermodule (8) receives the MPEG-4 flow and the complementary data from theportal (12).

In contrast, in the implemented example, instead of modifying everyI-VOP plane, the analysis system (121) only takes one I-VOP plane out ofn in which n is a random number comprised between 1 and 12, and takesinto account the P-VOP planes. Thus, prior to sending the MPEG-4 fromthe output buffer (122), the analysis system (121) will read theincoming MPEG-4 flow (101) and after drawing the random number n, thesynthesis system modifies the correlation coefficients at the nth I-VOPplane of the MPEG-4 flow. After each I-VOP plane modified in thismanner, the analysis system (121) will perform a new drawing of a randomnumber n. Each random number used in this manner is recorded in thebuffer (123) of the portal (12). For the P-VOP planes, the analysissystem (121) takes into account one P-VOP plane out of m in which m is arandom number comprised between 1 and 5, in a frame for which the I-VOPplane was not modified.

The analysis system (121) of the portal (12) reads the incoming MPEG-4flow (101) and whenever it detects an nth I-VOP plane or an mth P-VOPplane, it breaks them down into macroblocks (thus into slices), theninto blocks. This analysis allows it to recognize the DC coefficients inthe code and to substitute certain among them with random values inorder to render the planes (and by consequence the sequence) unreadablefrom the human vision point of view. The true values of the DCcoefficients will be stored in the output buffer (123) which willsubsequently enable the reconstitution of the original sequence in thedecoder module (8), by following the reverse schema.

Moreover, in this second implemented example, not all of the DCcoefficients of this nth I-VOP plane will be modified. Only onemacroblock out of two comprises a modified block (DC coefficient) whilerespecting the equality of the modification frequencies for the sixblocks of a macroblock. Moreover, the substitution of each DCcoefficient is performed by a DC coefficient calculated in a randommanner, but its value is compared to the value of the DC coefficient tobe substituted in a manner such as to verify its deviation. If thedeviation is too small, another random number is calculated so as toincrease the deviation between the coefficient to be substituted and thesubstitution coefficient.

The same is true for the P-VOP planes.

For the reconstitution of the MPEG-4 flow, the decoder module (8) readsthe buffers (86) and (87) and decodes the data elements of the binarytrain in accordance with the defined syntax.

When it reads the binary train, the decoder identifies the beginning ofa coded plane and then the type of plane. It decodes successively eachmacroblock of the plane. The macroblock type and the movement vectorsare used to construct a prediction of the current macroblock based onthe prior and future reference planes which were stored in the decoder.The data of the coefficients are decoded and dequantified. Each 8×8block of coefficient data is transformed by an inverse DCT. The resultis added to the prediction signal with a defined dynamic. Before sendingthe MPEG-4 flow to the reader (81), the synthesis system (87) replacesthe DC coefficients of the I-VOP and P-VOP planes that were substitutedwith those of the flow stemming from the buffer (86).

Upon reconstitution of the MPEG-4 flow by the synthesis system (87) ofthe decoder module (8), the reading of these random numbers andsubstituted correlation coefficients from the output buffer (123) of theportal (12) and the reading of the MPEG-4 flow modified in this mannerfrom the hard disk (85) of the decoder module (8) enable the synthesissystem (87) to reconstitute the I-VOP and P-VOP planes and to send allof this to the reader (81).

The plane is reconstructed by the reader (81) when all of themacroblocks have been processed. If it is dealing with an I-VOP or aP-VOP plane, it constitutes a reference plane for the subsequent planesand it is stored in place of the old reference plane. In the implementedexample for this user, it was found that the second flow demanded a passband smaller than one per thousand of the pass band required fortransmitting the high-quality MPEG-4 flow, i.e., less than one kilobitper second for the second flow compared to one megabit per second forthe first MPEG-4 flow.

We will now describe in detail the different steps for the third user.

The portal (121) selected the MPEG flow (101) that it must send to thedecoder module/user (8) to be watched on television screen (6) on adelayed basis. This user is linked to a digital cable broadcast network(4) with video on demand (VOD) available, the network (10) is thusidentical to the network (4). The analysis system (121) of the portal(12) will thus read the incoming MPEG-4 flow (101) and whenever itdetects an I-VOP plane, it searches for the first P-VOP plane thatfollows this I-VOP plane in order to replace it with a random P-VOPplane that it itself calculated. The new modified MPET-4 flow is thenrecorded in the output buffer (122) in order to be broadcast on thebroadcast network (4) via the link (5). The P-VOP planes taken from theincoming MPEG-4 flow (101) are stored in the memory of the buffer (123)of the portal (12). In the implemented example, rather than substituteeach P-VOP plane that follows an I-VOP plane, the analysis system (12)only takes one I-VOP plane out of n in which n is a random numbercomprised between 1 and 7. When the analysis system (121) writes thesubstituted P-VOP plane in the buffer (123), it also writes the numberof the I-VOP plane which precedes this substituted P-VOP plane. Theanalysis system (121) continues its analysis until the end of theincoming MPEG-4 flow.

During this time and in a completely unsynchronized manner, the modifiedMPEG-4 outgoing flow originating from the output buffer (122) of theportal (12) is broadcast via the broad-band network (4) to one or moredecoder modules/users (8).

Each decoder module (8) that wants to record this MPEG-4 flow modifiedin this manner can then read this MPEG-4 flow and record it on its harddisk (85). This recording initiative is left to the decoder module (8)under the control of the portal (12). In order to eliminate this, theanalysis system (121) wrote at the beginning of the MPEG flow aninformation unit of supplementary data that specified the destinationsof this modified MPEG flow. The destinations can thus be one sole andparticular addressee, a group of addressees or the totality of thedecoders modules (8) linked to the network (4).

The phase described above corresponds to the first preparation phase ofthe MPEG flow by the portal (12), to its transmission via the broad-bandnetwork (4) and to its recording in a decoder module (8). This decodercan then display this MPEG flow recorded on its hard disk. In order todo this, the synthesis system (87) of the decoder module (8) will readthe MPEG file from its hard disk (85) and then send it to a conventionalMPEG reader (81). If no complementary data are received by the synthesissystem (87), the MPEG flow that is received by the reader (81) isprocessed and displayed as it is, which creates a major distortion ofthe display on the visualization screen (6). In effect, the substitutedP-VOP planes which are processed by the synthesis system (87) do notcorrespond to the P-VOP planes which are necessary for a correctvisualization since these true P-VOP planes were substituted by randomP-VOP planes. In contrast, since the recorded flow is clearly a flow ofMPEG type, the standard reader (81) does not recognize any differenceand displays the information on the output screen (6) which appears bycontrast completely incoherent to the human watching the screen (6). Allcopies of the MPEG flow originating from the hard disk (85) of thedecoder module (8) will produce the same visual effect upon theirrestitution by an MPEG reader. Any use of this copy which would be illintentioned is thus doomed to failure.

When the user of the decoder module (8) wants to display on screen (6)the audiovisual program recorded on hard disk (85), the user sends arequest to the synthesis system (87) with a remote control in the samemanner as if dealing with a VCR or a DVD player presenting a menu on atelevision screen. The synthesis system (87) then sends a request to thehard disk (85) and begins to analyze the modified MPEG flow originatingfrom the hard disk (85) via the reading buffer (83). The synthesissystem (87) then establishes a link with the portal (12) via thetelecommunication network (10) which in our example is also the cablenetwork but which could have been a conventional telephone network or aDSL link.

Once this link has been established and during the entire duration ofthe display of the film or audiovisual program, the synthesis system(87) draws out from the buffer memory (123) of the server (12) thesubstituted P-VOP planes and the data corresponding to the positions ofthese P-VOP planes in relation to the I-VOP planes of the flow recordedon the hard disk (85). The P-VOP planes and these position dataoriginate from the synthesis system (87) via the input buffer memory(86) and are stored temporarily in the volatile memory (88) of thesynthesis system (87). From the modified MPEG flow which originates viathe buffer (83) and from the P-VOP planes and the associated date whichoriginate via the buffer (86) in the memory (88), the synthesis system(87) reconstitutes in reverse manner to the previously describedanalysis process the substituted P-VOP planes by the real P-VOP planesand sends the new MPEG flow reconstituted in this manner to the reader(81) to be displayed on the screen (6). Upon their use, the P-VOP planesto be substituted and the data associated with these P-VOP planes areerased from the volatile memory (88).

In the implemented example, before the portal (12) authorizes sendingthe P images and the associated data from its buffer (123), the portal(12) had verified that the user of the decoder module (8) was indeedauthorized to do so. In order to perform this step, the portal (12)reads the information contained on the smart card (82) of the decodermodule (8) and/or the serial number of the decoder module (8) andverifies that this user is indeed authorized to watch this audiovisualprogram. It was not until after verification that the P-VOP planes andthe associated data were sent from the buffer (123) to the decodermodule (8) corresponding to this user.

In the implemented user, the user had also made a private copy of hisaudiovisual program. The synthesis system (87) therefore wrote in a part(84) of the hard disk (85) complementary data as well as the number ofthe smart card (82) and/or the serial number of the decoder module (8)and the information tag “private copy” as data associated with thisaudiovisual program. Upon the next reading of this audiovisual program,the synthesis system (87) will analyze these associated data and willthus inform the portal (12) that the user of the decoder module (8) isimplementing a reading of the private copy. If this function isauthorized by the portal (12), the P-VOP planes and the associated datawill then be sent via the portal (12) to the buffer (86) as describedabove. In the contrary case, the data will not be transmitted and theuser of the decoder module (8) will not be allowed to watch thereconstituted MPEG flow.

In one particular case of this implemented example, the broadcastnetwork (4) is a satellite network and the telecommunication network(10) is an airwaves system of the local radio loop (LRL) type.

In a manner identical to the description above, the user of the decodermodule (8) will receive the MPEG flow and the complementary data fromthe portal (12). In contrast, prior to sending the MPEG flow from theoutput buffer (122), the analysis system (121) will read the incomingMPEG flow (101) and after drawing a random number n comprised between 1and 4, the synthesis system permutes the nth P-VOP plane which followseach I-VOP plane of the MPEG flow with the first B-VOP plane whichfollows this P-VOP plane. Each random number used in this manner isrecorded in the buffer (123) of the portal (12).

Upon reconstitution of the MPEG flow by the synthesis system (87) of thedecoder module (8), the reading of these random numbers from the portal(12) and the reading of the MPEG flow modified in this manner from thehard disk (85) of the decoder module (8) enables the synthesis system(87) to restore the B-VOP and P-VOP planes in good order and to send theentirety to the reader (81).

We will now discuss in detail the different steps for the fourthimplementation represented by FIG. 3.

In this implementation, the MPEG-4 flow is processed by the analysissystem (12) in the same manner as the MPEG-4 flow of the secondimplementation.

However, the first modified MPEG-4 flow is written and recorded on aphysical support (20) of the CD type from the output buffer memory ofthe analysis system (12).

The second flow is stored in memory in the buffer (123) and is alsomoreover recorded on a physical support (10 bis) of credit card formatconstituted by a smart card and a flash memory. This card (10 bis) willbe read by the card reader (82) of the device (80). The device (80) is aportable and mobile autonomous system. In the implementation, the device(80) comprises the synthesis system (87), the standard MPEG-4 reader(81), the two buffer memories (86) and (83) as well as the disk reader(85).

The device (80) moreover comprises an integrated screen (6 bis) of theflat screen type which allows the user to watch directly his audiovisualprograms on his autonomous device (80).

In order to visualize an audiovisual program of the MPEG-4 type, theuser of the device (80) introduces in his disk reader (85) a disk (20bis) of the type (20) identical to that recorded by the analysis system(12). This disk (20 bis) thus contains an MPEG-4 flow of the type of thefirst flow, i.e., with the DC coefficients of certain I-VOP and/or P-VOPplanes substituted.

The user of the device (80) can thus visualize this MPEG-4 flow on hisscreen (6 bis) integrated in his device. However, because of thesubstitution of the DC coefficients, the MPEG-4 flow will not be correctfrom the visual point of view. In order to render this flow correctvisually, the user introduces into the smart card reader (82) the memorycard (10 bis) containing the second flow with the DC coefficients. Thesynthesis system then reconstitutes the correct MPEG-4 flow from thefirst flow originating from the disk (20 bis) and the second floworiginating from the card (10 bis) connected to the reader (82).

In one particular setup, the smart card (10 bis) also contains theapplications and the algorithms which will be executed by the synthesissystem (87).

In another particular setup, the smart card (10 bis) contains the dataand the DC coefficients of multiple second flows for the reconstitutionof multiple MPEG-4 flows.

In one particular setup, the device (80) comprises a cellular link to aGSM network (10).

1. A method for distributing video sequences according to a nominal flowformat that describes a multiplicity of audiovisual scenes, each sceneincluding a multiplicity of hierarchized audiovisual objects and adescriptor of the hierarchy and of spatial and temporal relationshipsamong the objects, each video object comprising at least one completeintra-video object plane (I-VOP), comprising: analyzing a flow of videosequences; generating a first modified flow having the format of anominal flow and a second flow of any format comprising digitalinformation required for reconstruction of modified planes, based on theanalysis of the flow of video sequences; separately transmitting the twoflows generated from a server to destination equipment; and calculatingon the destination equipment a synthesis of a flow of the nominal formatas a function of the first and second flows.
 2. The method according toclaim 1, wherein each video object comprises at least one N-VOP plane,data representing the plane being calculated as a function ofdifferences between the N-VOP plane and at least one other plane.
 3. Themethod according to claim 2, wherein the first flow has modified N-VOPplanes.
 4. The method according to claim 2, wherein the data of at leastone N-VOP plane are calculated by movement compensation from the N-VOPplane in relation to a preceding N-VOP or I-VOP plane such that theN-VOP plane is a P-VOP plane (predicted).
 5. The method according toclaim 2, wherein data of at least one N-VOP plane are calculated bymovement compensation from the N-VOP plane in relation to preceding andfollowing P-VOP or I-VOP planes such that the N-VOP plane is a B-VOPplane (bidirectional).
 6. The method according to claim 1, wherein thenominal flow format is defined by the MPEG-4 standard.
 7. The methodaccording to claim 4 or 5, wherein the first flow has modified P-VOPplanes.
 8. The method according to claim 5, wherein the first flow hasmodified B-VOP planes.
 9. The method according to claim 4 or 5, whereinthe I-VOP plane is broken into blocks and macroblocks each dependent oneach other by correlation coefficients, the first modified flow havingI-VOP planes modified by substitution of selected correlationcoefficients by coefficients of the same nature, but random, and thesecond flow comprises substituted correlation coefficients and thedigital information needed to enable the reconstruction of the modifiedplanes.
 10. The method according to claim 1, wherein analyzingdetermines the correlation coefficients to be modified as a function ofa desired size for the second flow and a desired degradation for thefirst modified flow.
 11. The method according to claim 9, wherein atleast one P-VOP plane is modified in the same manner as the I-VOPplanes.
 12. The method according to claim 9, wherein analyzingdetermines the I-VOP, P-VOP and B-VOP planes to be modified as afunction of a desired size for the second flow and a level ofdegradation desired for the first modified flow.
 13. The methodaccording to claim 9, wherein transmission of the first flow isimplemented via a physically distributed material support.
 14. Themethod according to claim 1, wherein transmission of the first flow isimplemented via a broad-band network or DAB.
 15. The method according toclaim 1, wherein transmission of the second flow is implemented via aswitched telephonic network (analog or digital PSTN) or via a DSL typenetwork (Digital Subscriber Line) or via an LRL network (local radioloop) or via a mobile telephonic network using GSM, GPRS or UMTSstandards.
 16. The method according to claim 1, wherein transmission ofthe second flow is implemented via a physically distributed materialsupport.
 17. The method according to claim 1, wherein transmission ofthe second flow is implemented via a broad-band network of the same typeas the network used for the first flow.
 18. The method according toclaim 1, wherein transmission of the second flow is implemented via thesame broad-band network as used for the first flow.
 19. The methodaccording to claim 1, wherein transmission of at least one of the twoflows is encrypted.
 20. The method according to claim 1, wherein atleast one of the two flows is watermarked.
 21. The method according toclaim 1, wherein the two generated flows may be sent to a singleequipment unit or a group of equipment units.
 22. The method accordingto claim 1, wherein reconstruction and/or visualization is contingent ona transaction.
 23. The method according to claim 1, whereinreconstruction can be authorized by a consultation of a private copyrequested by a user.
 24. Apparatus for creating a video flow accordingto the method of claim 1, comprising at least one multimedia servercontaining original video sequences and a device for analyzing the videoflow originating from the server for generating the first and secondflows.
 25. The apparatus according to claim 24, further comprising amemory for recording a “private copy” marker indicating for eachsequence rights of each user selected from the group consisting of aprivate copy that can be watched an unlimited number of times, a privatecopy that can be watched a limited number of times with specification ofthat number, and private copying prohibited.
 26. The apparatus accordingto claim 24, further comprising a standard flow decoder, at least onerecording interface for storing contents of the first flow and at leastone display interface, and means for recomposing the original flow fromthe first and second flows.
 27. The apparatus according to claim 26,wherein the recomposing means is software on the server.
 28. Theapparatus according to claim 26, wherein the recomposing means issoftware installed on a smart card.
 29. The apparatus according to claim26, wherein the recomposing means is an electronic device.
 30. Theapparatus according to claim 28, wherein the recomposing means uses aresource specific to the smart card to prevent copying of temporaryinformation.
 31. The apparatus according to claim 26, wherein therecording interface also stores a “private copy” marker in relation tothe first flow indicating for this sequence a user's rights selectedfrom the group consisting of a private copy that can be watched anunlimited number of times, a private copy that can be watched a limitednumber of times with indication of that number, and private copyingprohibited.
 32. The apparatus according to claim 26, further comprisinga smart card reader enabling identification of a user when the userwants to watch an audiovisual program.
 33. Apparatus for exploiting avideo flow according to the method of claim 1, comprising a computerwhich is part of a communication interface for receiving a video floworiginating from a communication network or a physical support reader,and equipped with at least one recorder for storing the first flow, anda decoder comprising a display interface, communication means with thecomputer for receiving the first flow transmitted by the computer andcommunication means for receiving the second flow recomposing means forthe original flow from the first and second flows.
 34. The apparatusaccording to claim 33, wherein the recomposing means is softwareinstalled only on the decoder.
 35. The apparatus according to claim 33,wherein the recomposing means is an electronic device installed only onthe decoder.
 36. A system for transmitting a video flow according to themethod of claim 1, comprising an equipment unit for production of avideo flow, at least one equipment unit for exploitation of a video flowand at least one communication network between the production equipmentunit and the exploitation equipment unit(s).